Compounds for use as ligands

ABSTRACT

The present invention relates to compounds and their use as ligands, in particular, in metal catalyst complexes. The ligands of the invention are capable of binding to a solid support. The invention includes the ligands in their own right and when bound to a support and the compounds may be used to prepare metal catalyst complexes.

FIELD OF THE INVENTION

This invention relates to compounds and their use as ligands, inparticular in metal catalyst complexes. More specifically, the inventionis concerned with ligands that are capable of binding to a solidsupport. The invention includes the ligands in their own right and whenbound to a support. The ligands are used to prepare metal catalystcomplexes which are easy to recover. This feature aids catalystrecycling and also facilitates their use in flow processing. Thesefeatures lead in turn to improved efficiency and output.

BACKGROUND TO THE INVENTION

Many homogeneous catalysts are based on organometallic complexes, inparticular complexes comprising transition metals. Organometalliccomplexes comprising η-cyclopentadienyl ligands are particularly useful.This class of electron-rich aromatic ligand is often strongly bound tothe metal catalyst, resulting in stable complexes with significantsteric bulk around the metal centre. The pentamethylcyclopentadienyl(Cp*) ligand is commonly used in conjunction with transition metalcatalysts such as Ru, Rh, Ir, Ti and Fe. Although many benefits may bederived from such catalysts, the catalysts are expensive and thereforemay need to be recovered at the end of a reaction to enable economicuse. Homogeneous catalysts are, however, often difficult to separatefrom the product in a simple and economical fashion. To address theselimitations, attempts have been made to prepare cyclopentadienyl ligandswhich are bound to a solid support. However, many of these processesrequire a complex multi-step synthesis to produce the desired ligands.

WO 2007/096592 discloses a microencapsulated catalyst-ligand systemcomprising a polymeric ligand encapsulated within a permeable polymershell. This publication discloses inter alia the encapsulation ofcyclopentadienyl ligands, including1-(3-hydroxypropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-hydroxybutyl)-2,3,4,5-tetra methylcyclopentadiene,1-(5-hydroxypentyl)-2,3,4,5-tetramethylcyclo pentadiene,1-(3-aminopropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-aminobutyl)-2,3,4,5-tetramethyl cyclopentadiene,1-(5-aminopentyl)-2,3,4,5-tetramethylcyclopentadiene and 1-(8-heptadecenyl)-2,3,4,5-tetramethylcyclopentadiene.

SUMMARY OF THE INVENTION

The present invention provides ligands, including without limitationcyclopentadienyl ligands, which are capable of binding to a solidsupport. The solid supported catalysts produced in accordance with theinvention have a number of benefits including improved metal recovery,reduced metal contamination of reaction products, simpler productpurification and the potential for catalyst recycling. In addition, theimmobilised catalysts allow reactions to be run under flow conditionsrather than under batch conditions, which provides a number of benefitsin processing terms.

A further benefit of the catalysts is that the ligand environment aroundthe metal centre is well defined in the supported metal catalyst. Thisis a significant advantage relative to microencapsulated catalysts.

According to a first aspect of the present invention, there is provideda compound of the formula (I):

wherein

-   -   R¹ is an unsaturated carbocyclic group having five or six ring        carbon atoms;    -   X is a linker comprising at least two in-chain carbon atoms; and    -   Y is selected from ═O, ═S, —OH, —SH, —S(O), —S(O)₂, amino and        monosubstituted amino.

In a further aspect, the invention provides supported compounds of theformula (II):

wherein

-   -   R¹ and X are as defined in formula (I);    -   Y′ is selected from —O—, —S— and aminylene; and    -   Z is a support.

Also provided are metal complexes comprising, as a ligand, a compound offormula (I) or a compound of formula (II). Metal complexes of theinvention may comprise a metal catalyst, for example a transition metalcatalyst. Processes for the production of compounds of the invention andmetal complexes thereof are also provided.

Compounds of the invention may be used to prepare metal catalystcomplexes which are readily recoverable and which have desirablecatalytic activity. The resulting metal catalysts may be used tocatalyse a variety of reactions, for example transfer hydrogenation,dehydrogenation, metathesis or polymerisation processes. Furthermore,the compounds may be prepared from inexpensive and readily availablestarting materials via a limited number of processing steps.

DESCRIPTION OF VARIOUS EMBODIMENTS

In formulae (I) and (II), R¹ is an unsaturated carbocyclic group havingfive or six ring carbon atoms. The carbocyclic group may beunsubstituted or substituted by one or more (e.g. 1, 2, 3, 4 or 5)substituents. Exemplary substituents include optionally substitutedhydrocarbyl groups, e.g. optionally substituted C₁₋₂₀ alkyl (e.g. C₁,C₂, C₃ or C₄ alkyl), terpenes (e.g. menthyl, neomenthyl or limonenyl) oroptionally substituted aryl (e.g. phenyl) groups.

In a preferred embodiment, R¹ is an unsaturated carbocyclic group havingfive ring carbon atoms. In a particular embodiment, R¹ is acyclopentadienyl group. The cyclopentadienyl group may be unsubstitutedor substituted with 1, 2, 3 or 4 substituents. The substituents may beindependently chosen. Exemplary substituents include optionallysubstituted hydrocarbyl groups, for example selected from optionallysubstituted C₁₋₂₀ alkyl (e.g. C₁, C₂, C₃ or C₄ alkyl), terpenes (e.g.menthyl, neomenthyl or limonenyl) and optionally substituted aryl (e.g.phenyl) groups. In one embodiment, R¹ is cyclopentadienyl optionallysubstituted with 1, 2, 3 or 4 substituents independently selected frommethyl, ethyl and phenyl. In another embodiment, R¹ is cyclopentadienyloptionally substituted with 1, 2, 3 or 4 methyl groups. In a furtherembodiment, R¹ is tetramethylcyclopentadienyl. The cyclopentadienylgroup may be present in the form of one or more structural isomers, eachof which is encompassed by the present invention. The cyclopentadienylgroup may be in the form of a deprotonated anion and therefore maycomprise a cationic counterion.

In another embodiment, R¹ is an unsaturated carbocyclic group having sixring carbon atoms. The carbocyclic group may be aromatic ornon-aromatic; preferably it is an aromatic group. Examples includephenyl and naphthyl groups. Included are compounds in which R¹ is aphenyl group. The phenyl group may be unsubstituted or substituted with1, 2, 3, 4 or 5 substituents. Exemplary substituents include optionallysubstituted hydrocarbyl groups, for example selected from optionallysubstituted C₁₋₂₀ alkyl (e.g. C₁, C₂, C₃ or C₄ alkyl), terpenes (e.g.menthyl, neomenthyl or limonenyl) and optionally substituted aryl (e.g.phenyl) groups.

The linker X comprises at least two in-chain carbon atoms. Typically, Xis acyclic. In embodiments, each of the in-chain atoms of X isindependently selected from carbon, nitrogen, oxygen and sulphur.

In certain compounds, X is a hydrocarbylene linker optionallyinterrupted by one or more (e.g. 1, 2, 3 or 4) in-chain heteroatoms,e.g. selected from oxygen, nitrogen and sulphur. In other compounds, Xis a hydrocarbylene linker. The term “hydrocarbylene” as used hereinrefers to a linker having a chain consisting exclusively of hydrogen andcarbon atoms, wherein the chain may be unsubstituted or substituted withone or more (e.g. 1, 2, 3, 4 or 5) substituents. In one embodiment, X isa hydrocarbylene linker having from 2 to 20 (e.g. from 2 to 10) in-chaincarbon atoms. Where the hydrocarbylene chain is substituted, the one ormore substituents may, for example, be selected from amino, hydroxy,C₁₋₆ alkyl, C₁₋₆ alkoxy, carbonyl, carbocyclyl (e.g. aryl or C₃₋₆cycloalkyl) and heterocyclyl (e.g. heteroaryl) groups.

In one embodiment, X is an alkylene group or an alkenylene group, eitherof which is optionally interrupted by one or more (e.g. 1, 2, 3 or 4)in-chain heteroatoms. The term “alkylene” in this context refers to adivalent, straight or branched chain alkane group which is optionallysubstituted with one or more (e.g. 1, 2, 3, 4 or 5) substituents.

“Alkenylene” refers to an alkylene group having at least one doublebond, of either E or Z stereochemistry where applicable. In embodiments,X is an alkylene or alkenylene group, e.g. having from 2 to 20 (e.g.from 2 to 10) in-chain carbon atoms. Exemplary alkylene groups includeethylene, propylene (e.g. n-propylene), butylene (e.g. n-butylene) andpentylene (e.g. n-pentylene), any of which is optionally substitutedwith one or more (e.g. 1, 2, 3, 4 or 5) substituents. Exemplaryalkenylene groups include ethenylene, 2-propenylene, 1-butenylene,2-butenylene, 3-butenylene, 1-pentenylene, 2-pentenylene and3-pentenylene, any of which is optionally substituted with one or more(e.g. 1, 2, 3, 4 or 5) substituents. Where the alkylene or alkenylenechain is substituted, the one or more substituents may, for example, beselected from amino, hydroxy, C₁₋₆ alkyl, C₁₋₆ alkoxy, carbonyl,carbocyclyl (e.g. aryl or C₃₋₆ cycloalkyl) and heterocyclyl (e.g.heteroaryl) groups.

In formula (I), Y is selected from ═O, ═S, —OH, —SH, —S(O), —S(O)₂,amino and monosubstituted amino. Where Y is monosubstituted amino, theamino group may be substituted with, for example, an optionallysubstituted hydrocarbyl group (e.g. a C₁₋₆ alkyl, aryl or arylalkylgroup), a heterocyclyl group (e.g. a heteroaryl group) or aheterocyclylalkyl group, any of which is optionally attached to thenitrogen atom of the amino group via a linkage selected from —O—, —C(O)——C(O)O—, —S—, —S(O)— and —S(O)₂—. Exemplary monosubstituted amino groupsinclude N—(C₁₋₆ alkyl)amino, acetylamino and tosylamino groups. In oneembodiment, Y is selected from ═O, —OH and —NH₂.

In formula (II), Y′ is selected from —O—, —S— and aminylene. The term“aminylene” as used herein refers to an optionally substituted, divalentamine group. Included are compounds in which Y′ is —NH— optionallysubstituted with a hydrocarbyl group (e.g. a C₁₋₆ alkyl, aryl orarylalkyl group), a heterocyclyl group (e.g. a heteroaryl group) or aheterocyclylalkyl group, any of which is optionally attached to thenitrogen atom of the aminylene group via a linkage selected from —O—,—C(O)— —C(O)O—, —S—, —S(O)— and —S(O)₂—. Exemplary aminylene groupsinclude —NH—, —N(C₁₋₆ alkyl)-, —N(acetyl)- and —N(tosyl)- groups. In oneembodiment, aminylene is —NH—.

In a particular embodiment, the invention provides compounds of formula(I) in which —X—Y is selected from 2-hydroxyethyl, 3-hydroxy-n-propyl,4-hydroxy-n-butyl, 5-hydroxy-n-pentyl, 2-hydroxypropyl, 3-hydroxybutyl,3-hydroxy-1-methylpropyl, 1-methylene-3-hydroxypropyl,3-hydroxyprop-1-enyl, 3-hydroxy-3-phenylpropyl, 2-oxopropyl, 3-oxobutyl,4-oxopentyl, 3-aminopropyl, 5-aminopentyl, 3-propanoate and5-pentanoate. Also provided are compounds of the formula (II) derived byreacting said compounds of formula (I) with a solid support.

In another embodiment, the compound of formula (I) is not selected from1-(3-hydroxypropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-hydroxybutyl)-2,3,4,5-tetra methylcyclopentadiene,1-(5-hydroxypentyl)-2,3,4,5-tetramethylcyclopentadiene,1-(3-aminopropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-aminobutyl)-2,3,4,5-tetramethylcyclopentadiene,1-(5-aminopentyl)-2,3,4,5-tetramethylcyclopentadiene and1-(8-hepta decenyl)-2,3,4,5-tetramethylcyclopentadiene.

A compound of formula (II) may be obtained by reacting a compound offormula (I) with a support, e.g. a solid support, containing one or morefunctionalities which are capable of reacting with the moiety Y.Suitable supports and methods of attachment will be familiar to thoseskilled in the art. For example, where Y is oxo or thioxo, a supportcomprising one or more pendant amine functionalities may be employed.Where Y is hydroxy, a support comprising one or more pendant carboxylicacid or halogen groups may advantageously be used. Typically, theresulting compound will be bound to an outer surface of the support,e.g. to the surface of a polymer bead.

Supports include inorganic supports and organic supports, particularlypolymer supports. In embodiments, the support is a solid support.

Inorganic supports may be derived from naturally occurring inorganicmaterials or matrices or may be synthesised. Inorganic materials ormatrices include glasses, silicas, aluminas, titanates and hybrid oxidesthereof, graphites, oxides and zeolities.

Polymer supports may be derived from the polymerisation of a compositioncomprising one or more monomers, and are preferably derived from thepolymerisation a composition comprising of two or more monomers. Themonomers may contain one or more polymerisable double bonds. In oneembodiment, the polymer support is derived from the polymerisation of acomposition comprising one or more monomers containing only onepolymerisable double bond, and one or more monomers containing two ormore polymerisable double bonds. In another embodiment, the polymersupport is derived from the polymerisation of a composition comprisingone or two monomers containing only one polymerisable double bond, andone monomer containing two or three polymerisable double bonds. Examplesof monomers containing only one polymerisable double bond includestyrene and substituted styrenes such as a-methyl styrene, methylstyrene, t-butyl styrene, bromo styrene and acetoxy styrene; alkylesters of mono-olefinically unsaturated dicarboxylic acids such asdi-n-butyl maleate and di-n-butyl fumarate; vinyl esters of carboxylicacids such as vinyl acetate, vinyl propionate, vinyl laurate and vinylesters of versatic acid such as VeoVa 9 and VeoVa 10 (VeoVa is atrademark of Shell); acrylamides such as methyl acrylamide and ethylacrylamide; methacrylamides such as methyl methacrylamide and ethylmethacrylamide; nitrile monomers such as acrylonitrile andmethacrylonitrile; and esters of acrylic and methacrylic acid,preferably optionally substituted C₁₋₂₀ alkyl and C₁₋₂₀ cycloalkylesters of acrylic and methacrylic acid, such as methyl acrylate, ethylacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, i-propyl acrylate,and n-propyl acrylate, methyl methacrylate, ethyl methacrylate, n-butylmethacrylate, 2-ethylhexyl methacrylate, i-propyl methacrylate, n-propylacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate,N,N-dimethylaminoethyl acrylate and N,N-dimethylaminoethyl methacrylate.Functional derivatives of the foregoing monomers containing only onepolymerisable double bond can also be employed. Examples of monomerscontaining two or more polymerisable double bonds include divinylbenzene(DVB), trivinylbenzene, and multifunctional acrylates and methacrylatessuch as ethylene glycol diacrylate, ethylene glycol dimethacrylate,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,ethylene bisacrylamide, pentaerythritol triacrylate, pentaerythritoltetraacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate and N,N-bis-acryloyl ethylene diamine.

The solid support may be a macroporous resin. The term “macroporous”indicates a class of resins which have a permanent, well developedporous structure. Importantly, these resins can have much higher surfaceareas (as measured by nitrogen BET) in the dry state than gel typeresins. Typically, surface areas in the dry state can range from 50 to1000 m/g. Although there is no, universally accepted definition of amacroporous resin, in the case of styrene-DVB resins it has beensuggested that a macroporous resin may be defined as resin which in thedry state when exposured to cyclohexane exhibits a cyclohexane uptake ofat least 0.1 mg⁻¹ over 16 h (Millar, J. R. et. al., J. Chem. Soc., 1996,218). Macroporous resins are often formed when the compositioncomprising monomers containing two or more polymerisable double bonds ispolymerised in the presence of a porogen. The porogen causes phaseseparation of the polymer matrix. Removal of the porogen and dryingyields rigid, opaque, permanently porous beads. Phase separation iscontrolled by the nature and level of the porogen employed, and thelevel of crosslinking agent employed. By way of example, the solidsupport may be a macroporous chloromethyl resin.

The support may comprise a poly(ethylene glycol). The use of apoly(ethylene glycol)-based support may advantageously allow compoundsof the invention and metal complexes thereof to be separated from thereaction mixture, e.g. using membrane separation techniques. Inembodiments, the support comprises a poly(ethylene glycol) having anumber average molecular weight Mn of from about 100 to about 10000Daltons, e.g. from about 200 to about 5000 Daltons, in particular fromabout 200 to about 2000 Daltons. In a particular embodiment, Z comprisesa poly(ethylene glycol) and —X—Y′— is an ether or polyether chain.

The support may be in the form of one or more beads, for example one ormore polymer beads. In one embodiment, the solid support comprises oneor more beads having a diameter of from 10 μm to 2000 μm, e.g. from 50μm to 1000 μm, e.g. from 75 μm to 500 μm.

Also provided is a metal complex comprising a metal, e.g. a metalcatalyst, and one or more ligands, wherein at least one of the ligandsis a compound of formula (I) or a compound of formula (II). Compounds ofthe invention will generally coordinate to the metal via the group R¹. Ametal complex comprising a ligand of the formula (II) may be obtained byattaching a metal complex comprising a ligand of the formula (I) to asolid support via the moiety Y. Alternatively, the metal complex may beobtained by reaction of a compound of the formula (II) with a metal.

The metal complex preferably comprises a transition metal. For example,the metal may be selected from rhodium, iridium, platinum, palladium,titanium, ruthenium, cobalt and iron. Of particular mention as metalsare rhodium (e.g. rhodium (III)) and iridium (e.g. iridium (III)). Themetal complex typically comprises one or more additional ligands, forexample selected from halogen (e.g. chloro or iodo). The metal complexmay be in the form of a dimer.

The invention also provides a process for preparing a compound of theformula (I) in which R¹ is a cyclopentadienyl group. The processcomprises contacting a compound of formula (III):

wherein

-   -   X and Y are as defined in formula (I); and    -   each R² is independently an ethenyl group;        with an acid under conditions such that the R² groups and the        carbon atom together form a cyclopentadienyl group.

Each of the ethenyl groups represented by R² may be unsubstituted orsubstituted. In one embodiment, each R² is ethenyl optionallysubstituted with 1 or 2 substituents, for example selected fromoptionally substituted hydrocarbyl groups. Exemplary optionallysubstituted hydrocarbyl substituents include optionally substitutedC₁₋₂₀ alkyl (e.g. C₁, C₂, C₃ or C₄ alkyl), terpenes (e.g. menthyl,neomenthyl or limonenyl) or optionally substituted aryl (e.g. phenyl)groups. In another embodiment, each R² is ethenyl optionally substitutedwith 1 or 2 substituents selected from methyl, ethyl and phenyl. In afurther embodiment, each R² is 1,2-dimethylethenyl. Where an ethenylgroup is substituted, it may be of either E or Z stereochemistry whereapplicable.

The acid may be any suitable proton donor and is typically in aqueousform. By way of illustration, the acid may be aqueous hydrochloric acid.

The above process is carried out under conditions which promoteformation of a cyclopentadienyl group, rather than, for example, acyclopentenyl group. Thus, in embodiments, the process is carried outunder oxidizing conditions.

In one embodiment, the process further comprises contacting the compoundof formula (I) with a metal to form a metal complex of the invention.The process may further comprise attaching the resulting metal complexto a support via the moiety Y.

In an alternative embodiment, the process further comprises convertingthe compound of formula (I) to a compound of formula (II), by attachingthe compound of formula (I) to a support via the moiety Y. The processmay further comprise contacting the resulting compound of formula (II)with a metal to form a metal complex of the invention.

A compound of the formula (III) may be obtained by reacting a compoundof the formula (IV):

R²M  (IV)

-   -   wherein R² is as defined in formula (III) and M comprises a        metal;        with a compound of the formula (V):

-   -   wherein X is as defined in formula (III) and Y″ is —O—, —S— or        aminylene.

In one embodiment, the metal M comprises magnesium or lithium. Inanother embodiment, M is a magnesium halide, e.g. MgBr. Typically, thecompound of formula (IV) and the compound of formula (V) are contactedin an approximate molar ratio of 2 to 1.

Suitable reagents and conditions for conducting the various reactionsdescribed above are illustrated in the Examples described herein. Itwill be understood that the processes detailed herein are providedsolely for the purpose of illustrating the invention and should not beconstrued as limiting. A process utilising similar or analogous reagentsand/or conditions known to one skilled in the art may also be used toobtain a compound of the invention. Any mixtures of final products orintermediates obtained can be separated on the basis of thephysico-chemical differences of the constituents, in a known manner,into the pure final products or intermediates.

In a particular embodiment, the compound of formula (V) is a lactone,i.e. a compound in which Y″ is —O—. Exemplary lactones include thefollowing compounds:

The following Examples illustrate the invention.

Example 1 1-5-Hydroxypentyl)-tetramethylcyclopentadiene (Cp*C₅OH)

An oven dried three-necked 100 ml round bottom flask with refluxcondenser and dropping funnel attached was placed under a nitrogenatmosphere then charged with anhydrous diethyl ether (15 ml). Lithiumwire (0.90 g, 130 mmol, 3.2 mm diameter, 0.5-1% sodium) was washed withhexane, cut into small pieces and added to the reaction flask.2-bromo-2-butene (6.9 ml, 67.5 mmol, mixture of cis and trans isomers)was placed in the dropping funnel and a small portion added to thevigorously stirred lithium suspension. Once reaction had initiated,evidenced by refluxing of the solvent, the remaining 2-bromo-2-butenewas diluted with diethyl ether (20 ml) and added at a rate to maintain agentle reflux. After complete addition, the reaction mixture was stirredfor 1 h at r.t. Caprolactone (3.3 ml, 31.2 mmol) in diethyl ether (10ml) was then added dropwise. After stirring for a further 30 min, thereaction mixture was poured into sat NH₄Cl aq (120 ml), the ether layerseparated and the aqueous layer extracted with ether (2×40 ml). Thecombined ether layers were dried over MgSO₄ and concentrated to approx.30 ml. 10% Aqueous hydrochloric acid (50 ml) was added to theconcentrate and the two phase mixture stirred for 1.5 h at r.t. Theether layer was separated and the aqueous layer extracted with ether(2×30 ml). The combined ether layers were washed with water, dried overNa₂SO₄ and solvent removed to give a yellow oil. Purification by elutingthrough a plug of silica (heptane/EtOAc 4:1 as eluent) gave the productas a pale yellow oil (3.94 g, 61%). HPLC Retention time 7.8 min; ¹H NMR(300 MHz, CDCl₃) 3.63 (t, J=6.6 Hz, 2H, CH₂OH), 2.21 (m, 2H, CH₂), 1.81(s, 6H, 2×CH₃), 1.78 (s, 3H, CH₃), 1.59 (m, 2H, CH₂), 1.38 (m, 5H, 2×CH₂and allyl CH), 1.01 (dd, J=7.2, 3.3, 3 H, CH₃); GCMS (Trimethylsilylchloride added) 280.0 (M⁺+TMS) 7.49 min, 83%.

Example 2 1-(5-Hydroxypentyl)-tetramethylcyclopentadiene (Cp*C₅OH), byGrignard Formation

An oven dried three-necked 50 ml round bottom flask with refluxcondenser and dropping funnel attached was placed under a nitrogenatmosphere then charged with anhydrous THF (5 ml), magnesium turnings(0.59 g, 24.3 mmol) an one pellet of iodine. 2-Bromo-2-butene (2.3 ml,22.5 mmol, mixture of cis and trans isomers) was placed in the droppingfunnel and a small portion added to the vigorously stirred metalsuspension. Once reaction had initiated, evidenced by loss of the iodinecolour and refluxing of the solvent, the remaining 2-bromo-2-butene wasdiluted with THF (10 ml) and added gradually. A cloudy grey solutionformed. After complete addition, the reaction mixture was stirred for 1h at r.t. Caprolactone (1.1 ml, 10.4 mmol) in THF (5 ml) was then addeddropwise. After stirring for a further 30 min, the now yellow reactionmixture was quenched by the addition of 20% AcOH aq (10 ml). The organiclayer was separated and the aqueous extracted with ether (2×10 ml). Thecombined ether layers were stirred in a round bottom flask, 10% aqueoushydrochloric acid (20 ml) was added and the two phase mixture stirredfor 1.5 h at r.t. The ether layer was separated and the aqueous layerextracted with ether (10 ml). The combined ether layers were washed withsat NaHCO₃ aq then water, dried over Na₂SO₄ and solvent removed to givea pale yellow oil. Purification by eluting through a plug of silica(heptane/EtOAc 4:1 as eluent) gave the product as an almost colourlessoil (0.87 g, 40%). HPLC Retention time 7.8 min; GCMS (Trimethylsilylchloride added) 280.0 (M⁺+TMS) 7.49 min, 86%.

Example 3 1-(5-Hydroxypentyl)-tetramethylcyclopentadienyl DichloroRhodium (III) Dimer [RhCp*C⁵OHCl₂]₂

1-(5-Hydroxypentyl)-tetramethylcyclopentadiene (0.40 g, 1.92 mmol) wasdissolved in MeOH (4 ml) in a Radleys carousel tube and the solutiondegassed with nitrogen. Rhodium trichloride hydrate (0.252 g, 0.96 mmol)was added and the reaction mixture heated under nitrogen at reflux for24 h. After removal of the solvent on a rotary evaporator the redpowdery residue was dissolved in a minimum of DCM and productprecipitated with heptane and collected by filtration. Repetition ofthis precipitation process followed by vacuum drying at 40° C. gaveproduct as fine red crystals (0.340 g, 93%). HPLC Retention time 2.8min; ¹H NMR (300 MHz, CDCl₃) 3.63 (t, J=6.3 Hz, 2H, CH₂OH), 2.28 (m, 2H,CH₂), 1.64 (s, 6H, 2×CH₃), 1.62 (s, 6H, 2×CH₃), 1.57 (m, 2H, CH₂), 1.41(m, 4H, 2×CH₂).

Example 4 1-(5-Hydroxypentyl)-tetramethylcyclopentadienyl DichloroIridium(III) Dimer [IrCp*C₅OHCl₂]₂

By Conventional Heating

1-(5-Hydroxypentyl)-tetramethylcyclopentadiene (0.20 g, 0.96 mmol) wasdissolved in MeOH (4 ml) in a Radleys carousel tube and the solutiondegassed with nitrogen. Iridium trichloride hydrate (0.16 g, 0.45 mmol)was added and the reaction mixture heated under nitrogen at reflux for36 h. After removal of the solvent on a rotary evaporator the blackresidue was dissolved in a minimum of DCM and precipitated with heptane.The heptane was removed, DCM added to the solid and the brown solutionseparated from a black oily residue. Evaporation of the DCM solutionfollowed by precipitation from DCM with heptane gave the product as anorange solid (0.100 g, 47%). HPLC Retention time 3.2 min.

By Microwave Heating

1-(5-Hydroxypentyl)-tetramethylcyclopentadiene (0.19 g, 0.90 mmol) andsodium bicarbonate (42 mg, 0.5 mmol) were dissolved in MeOH (4 ml) in a5 ml capacity microwave tube and the solution degassed with nitrogen.Iridium trichloride hydrate (0.16 g, 0.45 mmol) was added and the tubesealed. Microwave heating was applied with a set temperature of 150° C.for 10 minutes. The reaction mixture was diluted with DCM (8 ml) thenwashed with water (6 ml) and the aqueous layer extracted with DCM (2×4ml). The combined DCM layers were dried over Na₂SO₄, solvent removed andproduct precipitated with heptane after dissolution in a minimum volumeof DCM. An orange solid was obtained (0.168 g, 79%). HPLC Retention time3.2 min.

Example 5 1-(5-Hydroxypentyl)-tetramethylcyclopentadienyl DiiodoIndium(III) Dimer [IrCp*C₅OHI₂]₂

Chloro iridium complex from experiment 4 (69 mg, 0.15 mmol Ir) andsodium iodide (22 mg, 0.60 mmol) were heated at reflux in degassedacetone (2 ml) under a nitrogen atmosphere. After 18 h, the solution wascooled, diluted with DCM (6 ml) and washed with water (6 ml). Theaqueous was extracted with DCM (2×2 ml), the combined organic layersdried over Na₂SO₄ and the solvent removed. Product was precipitated withheptane after dissolution in a minimum volume of DCM to give a brick redcrystalline solid, 75 mg (77%). Single crystal x-ray diffractionconfirmed the identity of this structure.

Example 6 Attachment to Quadrapure™ Resin

Ligands were attached to Quadrapure™ IDA resin bydiisopropylcarbodiimide, carbonyldiimidazole or thionyl chlorideactivation according to the following procedures.

Diisopropylcarbodiimide Activation

Quadrapure IDA beads (1.05 g, 7 mmol) were suspended in DCM (10 ml),diisopropylcarbodiimide (1.2 ml, 7.7 mmol) in DCM (5 ml) was added andthe reaction mixture stirred for 20 min at 40° C. Rhodium complex[RhCp*C₅OHCl₂]₂ of example 3 (76.1 mg, 0.2 mmol Rh) in DCM (4 ml) wasadded followed by DMAP (86 mg, 0.7 mmol) and stirring continued for afurther 18 h. MeOH (1 ml) was added to quench unreacted resin sites andafter an additional 1 h at 40° C. the beads were collected on a sinter(filtrate yellow), washed with DCM (2×10 ml), MeOH (2×10 ml) then DCM(4×10 ml). Vacuum drying gave pale orange beads of the rhodium supportedcomplex

Carbonyldiimidazole Activation

Quadrapure IDA beads (1.08 g, 7 mmol) were suspended in DCM (5 ml),carbonyldiimidazole (1.25 g, 7.7 mmol) in DCM (3 ml) was added and thereaction mixture stirred for 15 min at r.t. Rhodium complex[RhCp*C₅OHCl₂]₂ of example 3 (38 mg, 0.1 mmol Rh) in DCM (2 ml) wasadded and stirring continued for a further 20 min after which time MeOH(1 ml) was added to quench unreacted resin sites. The beads werecollected on a sinter (filtrate yellow), washing with DCM (4×10 ml) thenvacuum dried to give beads close in colour to the starting material.

Thionyl Chloride Activation

Quadrapure IDA beads (1.01 g, 7 mmol) were suspended in DCM (10 ml),thionyl chloride (2.6 ml, 70 mmol) was added and the reaction mixturestirred for 1 h at 40° C. The beads were filtered on a sinter and washedwith DCM (5×10 ml), before being resuspended in a round bottom flask inDCM (10 ml). Rhodium complex [RhCp*C₅OHCl₂]₂ of example 3 (76.1 mg, 0.2mmol Rh) in DCM (4 ml) containing N-diisopropylethylamine (1.2 ml, 14mmol) was added and the reaction mixture stirred at 40° C. for 18 h.MeOH (1 ml) was added to quench unreacted resin sites and after anadditional 1 h at 40° C. the beads were collected on a sinter (filtrateyellow), washed with DCM (2×10 ml), MeOH (2×10 ml) then DCM (4×10 ml).Vacuum drying gave pale orange beads of rhodium supported immobilised.

Example 7 Attachment to 2-Chlorotrityl Resin

Rhodium complex [RhCp*C₂OHCl₂]₂ of example 3(77.6 mg, 0.2 mmol Rh) wasdissolved in DCM (4 ml) and N-diisopropylethylamine (0.52 ml) added.This solution was added to an oven dried flask containing 2-chlorotritylchloride resin (1.007 g, 1 mmol), washing in with a further portion ofDCM (2 ml). The flask was flushed with nitrogen, stoppered and incubatedat 35-37° C. for 24 h. The resin was collected by filtration and washedwith DCM (5 times) then quenched with 10% N-diisopropylethylamine inMeOH before further washes with DCM (10 times) and MeOH (5 times). Theresin was vacuum dried to yield dark red beads of rhodium supportedcomplex.

Example 8 Use of Supported Catalysts in a Transfer HydrogenationReaction

Supported catalysts of Examples 6 and 7 were used to catalyse thetransfer hydrogenation of6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline. As FIG. 1 illustrates,the supported catalysts gave an equivalent enantiomeric excess (ee) tothe homogeneous catalyst. No leaching of coloured metal species wasobserved from the supported catalyst and a second use of the beads gaveessentially the same enantiomeric excess.

1.-21. (canceled)
 22. A metal complex comprising a metal and one or moreligands, wherein at least one of the ligands is a compound of theformula (I):

wherein R¹ is a cyclopentadienyl group; X is a linker comprising atleast two in-chain carbon atoms; and Y is selected from ═O, —OH, ═S,—SH, —S(O), —S(O)₂, amino and monosubstituted amino.
 23. A metal complexaccording to claim 22 with the proviso that the compound is not selectedfrom 1-(3-hydroxypropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-hydroxy butyl)-2,3,4,5-tetramethylcyclopentadiene,1-(5-hydroxypentyl)-2,3,4,5-tetramethylcyclopentadiene,1-(3-aminopropyl)-2,3,4,5-tetramethylcyclopentadiene,1-(4-aminobutyl)-2,3,4,5-tetramethylcyclopentadiene,1-(5-aminopentyl)-2,3,4,5-tetramethylcyclopentadieneand 1-(8-heptadecenyl)2,3,4,5-tetramethylcyclopentadiene.
 24. A metalcomplex according to claim 22, wherein R¹ istetramethylcyclopentadienyl.
 25. A metal complex according to claim 22,wherein X has from 2 to 20 in-chain carbon atoms.
 26. A metal complexaccording to claim 22, wherein X is an alkylene group or an alkenylenegroup.
 27. A metal complex according to claim 23, wherein Y is selectedfrom ═O, —OH and —NH₂.
 28. A metal complex according to claim 22,wherein Y is a monosubstituted amino and the amino group is substitutedwith an optionally substituted hydrocarbyl group, a heterocyclyl groupor a heterocycloalkyl group, any of which are optionally attached to thenitrogen atom of the amino group via a linkage selected from —O—, C(O)—,—C(O)O—, —S—, —S(O)— and —S(O)₂—.
 29. A metal complex according to claim28, wherein the amino group is substituted with an optionallysubstituted C₁₋₆ alkyl, aryl, arylalkyl or heteroaryl group.
 30. A metalcomplex according to claim 28 wherein the mono substituted amino groupis N—(C₁₋₆ alkyl)amino, acetyl amino and tosyl amino.
 31. A metalcomplex according to claim 22 wherein X—Y is selected from2-hydroxyethyl, 3-hydroxy-n-propyl, 4-hydroxy-n-pentyl, 2-hydroxypropyl,3-hydroxybutyl, 3-hydroxy-1-methylpropyl, 1-methylene-3-hydroxypropyl,3-hydroxy-3-phenylpropyl, 2-oxopropyl, 3-oxobutyl, 4-oxopentyl,3-aminopropyl, 5-aminopentyl, 3-propanoate and 5-pentanoate.
 32. A metalcomplex according to claim 22, wherein the metal is a transition metal.33. A metal complex according to claim 22, wherein the metal is selectedfrom rhodium, iridium, platinum, palladium, titanium, ruthenium, cobaltand iron.
 34. A metal complex according to claim 33, wherein the metalis selected from rhodium or iridium.
 35. A metal complex as claimed inclaim 22, wherein the metal complex comprises one or more additionalligands.
 36. A process for the production of the metal complex of claim22 comprising i) contacting a compound of formula (III):

wherein X and Y are as defined in claim 1; and each R² is independentlyan ethenyl group; with an acid under conditions such that the R² groupsand the carbon atom to which they are attached together form acyclopentadienyl group; and ii) contacting the compound of formula (I)with a metal to form the metal complex.
 37. A catalyst comprising themetal complex of claim 1.